In the field of professional cinematography, it is necessary under many circumstances that two lengths of film be kept in close and accurate register with one another throughout a lengthy continuous path. For example, in manufacturing a dye transfer print of a motion picture from three dye imbibed photographic matrices, it is essential that the dye image from each individual matrix be transferred to a receiver film in near perfect register with each other in three consecutive steps on a continuous machine. Further, it is also essential that each individual record is transferred completely from matrix to receiver film with substantially no movement of one film relative to the other, until such time as all of the image has been transferred from each individual matrix to the common receiver.
Previously, matrix and receiver films were placed in intimate contact with each other via a multi-stage seating mechanism generally known as a roll tank. While being placed into intimate contact with each other, the two films were also seated onto a stainless steel ribbon, known as a pin belt. The pin belt typically traveled in an orbital path extending around and between two or more drums or wheels. The perforations or sprocket holes of the sandwiched films were placed over silver alloy pins raised above the flat stainless steel ribbon. Both films remained firmly seated on the pin belt for the duration of time needed for complete dye transfer from matrix to receiver, generally about thirty five seconds.
Because of the time required for complete dye transfer, such pin belts generally had a peripheral length of about 205 feet and were operated at speeds of about 330 feet per minute. One of the difficulties resulting from using such long belts is achieving and maintaining the exacting pin tolerances necessary to hold the precise registration needed to produce high quality prints. In addition, repair and replacement of these long belts was indeed expensive and difficult. The machinery and methods used for dye transfer of color film prints has remained substantially unchanged since its original development in the 1920's and 1930's.
To obtain the faster throughput necessary to meet the demand for the larger quantities of prints required today, the operating speed of a dye transfer machine must be increased. A larger apparatus requiring a longer pin belt, however, would only magnify the problems of maintaining the exacting pin tolerances necessary to maintain precise registration during dye transfer. The space required for such an apparatus and the cost to manufacture and maintain the pin belt generally render such a system commercially impracticable.
For these and other reasons, the dye transfer process generally has become less favored than photographic copying processes. Conventional photographic copying of a master onto unexposed photographic films, such as nitrate, acetate, and more recently polyester films, are now widely used for producing the large number of prints needed for modern theater distribution, which can require more than 4,000 prints per film.
Photographic film processing, however, does not provide the precise color control of tone scale and color reproduction available using dye transfer processing, which may result in inferior color rendition in photographic film prints. Further, photographic film has a greater tendency to fade over time, resulting in a less durable print.
Accordingly, there is a need for an improved system for producing dye transfer prints of motion pictures that is capable of maintaining precise registration at high volume production speeds.
There is also, then, a need for a method of producing dye transfer prints of films competitively in sufficient quantities for the continuously growing need of motion picture theater distribution.